The present invention relates generally to the field of data storage systems, and more particularly to allocating migration files in hierarchical storage systems, such that a recall operation can be started within a predetermined time from which a recall request is received.
In a hierarchical storage management system, data is stored in different types of storage devices depending upon the frequency of usage of the data. For example, a system may include multiple storage media types to store data having different usage patterns and likelihoods of access. More frequently used data may be stored on direct access storage devices (DASD) comprising high-performance rapid access storage devices, such as hard disk drives. Less frequently used data may be archived on slower and less expensive, demountable storage media, such as optical disks and magnetic tape cartridges.
Two common functions initiated by host systems in hierarchical storage management systems include migration and recall. Migration typically involves the movement of data from a rapid access storage device, such as a hard disk drive, to a slower access storage device, such as a tape medium. A recall operation generally involves data transfer in the opposite direction (i.e., from a tape medium to a rapid access storage device).